For several years, we have been charting with fascination the historical data developed by Professor Jeremy Siegel of the University of Pennsylvania's WhartonSchool and used in his classic book &quot;Stocks For The Long Run.&quot;

Siegel's data and much else is available on his Web site. Note: He doesn't always agree with our interpretation of his work.

Through heroic calculation, Siegel has established the cumulative real return in key financial vehicles going back to 1801.

In other words, his data shows what would have happened on average to one dollar invested in each of these assets in 1801 -- adding in each year's capital gains, dividends and interest, and also adjusting for inflation.

In today's column, the first of three in a special series this week, we show the overall picture for stocks, bonds, treasury bills, gold and cash -- what would have happened to the value of a dollar bill that was just put in the mattress.

On Wednesday, we will zero in on what data says about the stock market now. We think it's bearish, or at least not very bullish.

On Friday, we will focus on bonds and bills. That's the chart that we think spells a return to inflation.

We will also report what Jeremy Siegel thinks, if we can intercept him as he whizzes around the country lecturing and consulting.

So as not to strain your eyes, we show in the top left corner what one dollar invested in stocks, bonds, bills, gold and cash would be worth now.

A dollar invested in stocks would now be worth $462,502 in 1801 dollars -- or $6.96 million in 2003 dollars. (Taxes are not included).

By contrast, a dollar bill kept under the mattress would be worth only 7 cents in 1801 dollars.

That's a measure of the two-century impact of inflation -- roughly 15-fold inflation since 1801.

The chart uses a log scale. That is, increases are proportionate. A steady increase shows as a straight line.

You can see right away why Siegel's book has its title. The total inflation-adjusted cumulative value of stocks has increased at a remarkably stable rate. The trendline on this chart -- which is actually a regression line, a statistical method of averaging the annual observations -- increases at a rate of 7 percent a year.

This is the fundamental reality underlying the late-1990s mantra that all you have to do is buy stocks and hold them.

It's true -- in the long run. But what about the short run?

We'll look at that on Wednesday. For now, however, note that the total cumulative return line for stocks, which ran up above the long-run trend line in the late 1990s, is finally back down just below it.

We read that to mean that stocks are not as overextended as they were -- but they're by no means undervalued.

Two other points:

Note the astonishing stability of gold. A dollar invested in gold in 1801 is worth just over a dollar today. Of course, the chart shows that gold's real price fell well below $1 in mid-20th century. But that's because the nominal price of gold was controlled by the federal government. Gold rebounded once the price was freed. Overall, it really does seem to be a store of value. Something to remember if inflation returns. Note that it would be impossible to draw a regression line through bonds, bills and cash. All of them inflect at the beginning of the 20th century - in the case of cash, sufficiently sharply to lose most of its value.

That's a hint as to why we think inflation will return.

Editor's note: The April edition of the Hulbert Financial Digest is now available by either e-mail or regular mail. Highlights this month include:

A special report on how the most popular stock picks by newsletter editors outperform the market, and what they are. Profiles of Timer Digest and John Dessauer's Investors World Complete performance scorecard, and more

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